We have a situation where some interceptor valves on one of our 500 megawatt steam turbine generation sets have been sezing following a recent outage. These are a fairly standard design with a hydraulic actualtor oprating the steam valve through a lincage system coupled to a crosshead or guide bush if you like which is fixed to the top of the valve spindle. This bush is approximately 6 inches in dia and about 6.5 inches long. It is here where we believe that the problem is occuring. (it is not the servo as the valve remained jammed following servo removal!)
We are looking into issues surrounding the lubrication of these bushings and mechanical limits and fits. We have been led to believe that the bushes have around 4 thou clearance which is somewhat less than the normal clearance of 10-15 thou.
My question is does anyone have any experience for minimum clearances for grease lubrication for this type of application. Obviously if the grease cannot 'wet' the entire circumference of the bush then problems are going to occur?
regards
Gary
We are looking into issues surrounding the lubrication of these bushings and mechanical limits and fits. We have been led to believe that the bushes have around 4 thou clearance which is somewhat less than the normal clearance of 10-15 thou.
My question is does anyone have any experience for minimum clearances for grease lubrication for this type of application. Obviously if the grease cannot 'wet' the entire circumference of the bush then problems are going to occur?
regards
Gary